The present invention relates to a thermally-insulating coating system for curved and/or hardened glass panes comprising at least one layer of noble metal enclosed by a lower and an upper blocker layer.
In another aspect, the present invention relates to the method of depositing the heat insulating layers onto a glass pane or panel and the production of glass products, such as automotive glass therefrom.
It is known in the art that coating systems can be applied to flat glass panes, that is, onto the flat glass. The coated flat glass is then heated up to just below its softening temperature and hardened by a shock-like cooling off. The curving or bending of the glass panes takes place between the heating and the quenching.
Thermally reflecting coating systems are known in which the glass panes are curved and/or hardened after the application of the coating system. For heat reflection one or several coatings of noble metal, e.g. silver on account of its good selective reflection capacity even at low coating thicknesses, is customarily used.
It is furthermore generally known that highly refractive dielectric layers can be arranged above and below the silver layer in order to improve the optical qualities. During the application of, for example, a metal-oxide layer on the silver and during the curving and/or hardening of the coated glass substrates with the associated heating, oxidation of the silver coating and diffusion of the silver into the metal-oxide coating tends to occur. The oxidation is caused by the fact that during the reactive application of the metal-oxide layer the oxygen that leaks in reacts with the silver. Also, during the heating of the coated glass panes the oxygen of the metal-oxide layer is activated and also unites with the silver. In addition, the diffusion of the silver is increased, as a result of which the thickness of the silver layer decreases. The reflection power of the coated glass panes is reduced by the oxidation and diffusion that takes place.
A coating system for curved and/or hardened glass panes is known (DE 196 32 788) which consists of dielectric layers, intermediate layers and at least one noble-metal layer. A dielectric layer, a metallic intermediate layer, a silver layer, another metallic intermediate layer and a dielectric layer following the coating system are successively sputtered by atomization onto the flat glass pane and the metallic intermediate coatings consist of an alloy of AlMgMn.
Furthermore, a multi-layer structure is known with selective light transmittency (EP 0,035,906) consisting of a substrate layer A, with a transparent laminar structure which carries a layer D which contains silver metal, has a thickness of 50 to 300 .ANG. and reflects infrared waves, as well as a transparent thin layer B.sub.1, with a high degree of refraction between layers A and D and/or a transparent thin layer B.sub.2 with a high index of refraction for layer D and, selectively, a transparent cover layer E on layer B.sub.2 (if present) or layer D; a layer C, consisting of a material which was selected from the group consisting of Ti, Zr, In, Si, C, Co and Ni and has a thickness of 3 to 100 .ANG., on layer D stands in contact with the latter on its side opposite layer A.
A glass pane with a transparent film is also known (EP 0,304,234) which film comprises a metal coating sensitive to tarnishing in the presence of an agent which causes tarnishing, and which film comprises a separate blocking layer which is further removed from the surface of the glass pane than is the metal layer. The blocking layer comprises metal-oxide layers including a layer of an oxide of a metal Me 1 which is located between layers of an oxide of a metal Me 2. Me 1 is titanium, zirconium or hafnium or a mixture of them and Me 2 is zinc, tin, indium or bismuth or a mixture of them.
Finally, a glass object, coated by sputtering a glass substrate is known (EP 0,722,913) which has a system consisting of the following layers, oriented outward from the glass:
A layer coating of Si.sub.3 N.sub.4 with a thickness of 300 to 500 .ANG.;
a layer of nickel or nickel chromium with a thickness of approximately 7 .ANG. or less; PA1 a layer of silver with a thickness of approximately 70 to 130 .ANG.; PA1 a layer of nickel or nickel chromium with a thickness of approximately 7 .ANG. or less; and PA1 a layer of Si.sub.3 N.sub.4 with a thickness of 700 to 1100 .ANG.; PA1 a layer of nickel or nickel chromium with a thickness of approximately 7 .ANG. or less; PA1 a layer of silver with a thickness of approximately 70 to 90 .ANG.; PA1 a layer of nickel or nickel chromium with a thickness of approximately 7 .ANG. or less; and PA1 a layer of Si.sub.3 N.sub.4 with a thickness of 350 to 700 .ANG..
An object of the present invention is to enable the deposition by sputtering of a thermally insulating layer and the tempering and curving of a glass substrate without significantly changing the optical qualities of the combination of the layers. In particular, the haze (diffuse scatter) should be less than 0.5 after the tempering.